Amplification and reproduction of electrical impulses



R.'H. RANGER June 18, 1929.

AMPLIFICA TI ON AND REPRODUCTION OF ELECTRICAL IMPULSES Filed Nbv. 4. 1924 2 Sheets-Sheet l TIME , INVENTOR RCHARD H. RANGER 1 5% ORNEY TIME MRSREQSY June 18, 1929. R RANGER 1,717,624

AMPLIFICATION AND REPRODUCTION OF ELECTRICAL IMPULSES Filed Nov. 4. 1924 2 Sheets- Sheet 2 WM M M 0U TPI/ 7 FROM TR/ODES RELAY OUTPUT h r 1 IINVENTOR mums H. RANGER ATTORNEY Patented June 18, 192 9.

UNITED :STATES RICHARD H. RANGER, F NEWARK, NEW JERSEY, ASSIGNOR TO RADIO 1,717,624 PATENT OFFICE.

conronnron OF AMERICA, A CORPORATION OF DELAWARE.

AMPLIFICATION AND REPRODUCTION OF ELECTRICAL IMPULSES.

Application filed November 4, 1924. SerialNo. 747,800.

My invention relates to electrical systems of the signalling type and especially to an improved amplifying relay system employing the so-called push-pull principle of amplification. My invention also relates to amplification and signalling methods.

Amplifying relay systems heretofore employcd possess the disadvantage of sluggish operation owing to transient conditions inherent in the systems themselves and in the systems with which they are associated with a resulting distortion of the signals especial- 1y at comparatively high keying frequencies.

One-of the principal objects of my invention is the provision of an amplifying relay system in which the above disadvantage is obviated.

Another principal object of my invention is the provisionof an improved amplifying re lay system possessing the following advantages: v

1) The establishment of a substantially in phase relationship bet-ween the si nal impulses and the corresponding ampli ed current impulses over a considerable range of keying frequencies for a given setting of the adjustable elements. j

(2) Faithful reproduction of the signal impulses greatly amplified with the substantial elimination of distortion over a considerable range of keying frequencies.

(3) Faithful reproduction, if desired, of substantially all impulses including both signal impulses and interfering impulses.

(4.) The elimination of the effects of certain kinds of static on'the amplified signal impulses.

(5) Speed in the reception of signal impulses.

- (6) The realization of very quick relay action by the production of amplified impulses having strong initialamplitudes followed by a tapering ofi of said initial amplitudes with the quick termination of the amplitudes at the proper time.

(7) The production of purified amplified impulses to produce positive action from Weak and uncertain signal impulses.

Other objects and advantages of my invention will be apparent from the following description taken in connection with the ac companying drawing in which Fig. 1 is a schematic diagram of a preferred embodiment .of my improved push-pull amplifying relay system.

Figs. 2, 3, 4, 5, and 6 are diagrammatic illustrations of the manner in which my system functions.

Referring to Fig. 1 two signal input leads 1 and 2 connect the out-put terminals of the source of received signal impulses to the outer extremities of resistances R and R respectively which are connected together at their inner extremities by lead 3.

My improved amplifying system comprises two triodes T and T The plate filament circuit of triode T comprises the following elements connected in the following manner a lead 4 connects the upper extremity of resistance R to one extremity of resistance R the other extremity of resistance R being connected to the minus terminal of the plate battery B The plus terminal of plate battery B is connected to one extremity of relay coil 6 by lead 7. The other extremity of coil 6 is connected to the plate element of triode T through a resistance R havinga variable condenser C connected in shunt therewith as shown. The filament of triode T is connected to the junction point of resistances R and R by lead 8 as shown.

The plate filament circuit of triode T comprises the following elements connected in the following manner; a lead 9 connects the lower extremity of resistence R to one extremity of resistance R theother extremity of resistance R being connected to the -minus terminal of plate battery B The plus terminal of plate battery B is connected to one extremity of relay coil 10 by lead 11. The other extremity of coil 10 is connected to the plate element of triode T through a resistance R5 having a variable condenser C in-sliunt therewith as shown. The filament of triode T is connected to the junction point of resistances R and R by the lead 8 as shown.

The filamentv currents for the two triodes may be supplied from the common source A, independent control of the individual filament currents being accomplished by means of the variable rheostats 1' as shown. The condensers C and C are preferably simultaneously controlled by a single control means as shown. However, I do not limit myself to such a control'means as-it is obvious that the condensers may be controlled independently (if each other if desired.

The grid element of triode T is connected to the plus terminal of the biasing battery C the minus terminal of said battery being con- C the plus terminal of said biasing battery being connected to thejunction point of resistance R and the minus terminal of plate battery 13,. 7

The resistance R, is preferably made equal to the resistance R the resistance R to R and the resistance R to R ,However, I do not limit myself to such an apportionment of resistance values, but may appropriately vary the relationship between the values of said resistances depending on the characteristics desired.

The biasing battery C is arranged ,to give the grid of triode T a more positive bias than C 'gives to the grid of triodeT The relay 5 comprises coils 6 and 10 for rocking the pivoted armature 12 to cause a movable contact 13 to alternately contact with the stationary contacts 14 and 15 which maybe employed for marking and spacing contacts. The contacts of the relay 5 may control any impulse or signal responsive device such as atelegraph sounder, telephone receiver, printing mechanism, retransmitting system, etc.

The above described system functions in the following manner: Assume that no signal impulses are being received. Owing to the fact thatthe grid element of triode T has more of a positive bias than that of triode T because of the extra biasimparted to it by the battery 6 more current will flow in its platefilament circuit. This current will: cause a slight energizing of relay coil 6 and a voltage drop through the resistances R and R Due to this voltage drop the grid element of triode T will have a negative bias imparted to it and consequently a condition is quickly set up Bf no current flowing in the plate-filament circuit of triode T and full plate current in triode T e The inductances of the relay coils 6 and 10 and the capacities'of the condensers C and C substantially determine the time constants of theplate-filament circuits of triodes T and T respectively. The time constants of the plate-filament circuits of triodes T and T are appropriately adjusted to the frequency of the signal impulses impressed on the system by suitable. adjustment of the condensers C and C However, thetriodes T and T are prevented .from functioning as oscillation generators by asuitable value of v the biasing batteries C and C Referring to Fig. 2, assume a signal pulse representing say a clash is impressed on the resistances B, and R The current 'due to this pulse, which attains its average ampli-' tude very suddenly and maintains the same for some length of time, causes a sudden voltage drop through the resistances R, and H This voltage drop makes the grid element of T less negative than it was before and the grid element of T negative rather than positive as it was before. The current at once starts to flow in the plate-filament circuit of triode T graphically represented'by curve Z) while the simultaneous diminution of current takes place in the plate-filament circuit of triode T graphically represented by curve a.

The plate-filament circuit current of triode T then effects a voltage drop through the resistances R and R which further decreases the plate-filament circuit currentof triode T and further increases the plate-filament circuit current of triodeT This action of course, takes place rapidly owing to the fact that practically only resistances are present in the system which comprises substantially no inductive reactance.

The decrease of the plate-filament current of triode T and the increase of the plate filament circuit current of T is accentuated by the condensers C and 0 respectively. A few instants later the plate-filament circuit current of triode T tapers off to a lower steady value as shown by curve 6 at d owing to the disappearance of the transient conditions created by the extra charge on condenser G which permitted the initial extra.

flow of current at the start and the limiting action of the resistance R, in maintaining a substantially lower but steady current for the remainder of the pulse,

The sudden decay of current in the platefilament circuit of triode T results in the sudden de-energization of relay coil 6; whereas the sudden increase of the plate-filament circuit current of triode T to its maximum amplitude causes a sudden energization of relay coil 10 resulting in the vigorous movement of the armature 12' to effect contact bethe power required to effect the quick movement of the armature 12.

As soon as the signal pulse disappears, the

voltage drops in the resistances R, and R disappear; the grid element of triode T again becomes negative while the grid element of triode T again becomes positive. The current in the plate-filament circuit of triode T suddenly decays to zero as shown by curve I) while the current in the plate-filament of circuit of T suddenly builds up to its maximum amplitude as shown by curve 0 owing to the action of the condensers C and C respectively.

The coil 10 of relay 5 is thus suddenly deenergized while the coil 6 is suddenly energized to its maximum value resulting in the vigorous movement of armature 12 to effect contact between the contacts 13 and 14.

The current in the plate-filament circuit of T a few instants later tapers olf to a lower value as shown by curve 0 owing to the disappearance of the transient conditions created by the condenser C and the influence of the resistance R A decreased energization of coil 6 therefore results as shown by curve 0. It is thus seen that the sudden maximum energization of one coil of the relay is effected while the other coil is simultaneously quickly tie-energized, this maximum energization tapering off to a lower holding value a few instants later resulting in quick and positive relay action. The system is now ready for the reception of another signal impulse.

Curves a, b and c of Fig. 3 corresponding to curves a, b and 0 respectively of Fig. 2,

graphically represent the functioning of the same system upon the reception of a dot impulse instead of a dash impulse.

It is obvious that the shapes of the transient portions of the curves shown in Figs. 2 and 3 may be modified within rather wide limits to obtain the desired advantages for different signalling conditions.

For example the faithful amplification and reproduction of all the impulses including both signal impulses and interfering impulses may be desired. In this case a very perfect relay action will be necessary in order that the amplifying system may closely follow all of the actual impulses impressed on it such as for example the impulses due to static as well as the signal impulses. To accomplish this result the condensers C and C should have small capacity values in order that the transient current surges may be of very short duration. In fact for absolutely faithful amplification and reproduction the condensers C, and C ma be eliminated entirely in order that the amplifying system may have a very high time constant resulting in the substantially instantaneous response to all impulses impressed thereon.

It has long been thought that reliance could not be placed on mechanical relay action for the faithful reproduction and amplification of received impulses. It has also been thought that errors would he introduced in the reception of radio telegraphic signals by the use of relays due to the fact that static pulses would be lengthened out and merged into each other to make false dots and dashes resulting in the reception of faulty signals. However, the above mentioned conclusions are based on the action of relays employed in the usual telegraphic systems where the action is relatively very sluggish as compared with the short pulses characteristic of static encountered'in radio signalling systems.

The relay 5 is preferably of the usual records obtained by two sensitive siphon recorders of the pulses in the input and output, respectively, of the amplifying relay system. The ordinates of Figs. 4 and 5 represent energy amplitudes while the abscissae represent time. It is readily seen from a perusal of Figs. 4 and 5 that all but the smallest pulses are recorded in the output of the amplifying system.

The mechanical relay 5 closes at each pulse and gives a true picture of the value of each pulse by reason of the fact that the marking contacts remain closed for such a short period of time that the recording arm of the siphon recorder does not have suificient time to rise,

to its full value. In other words a condition has been established where the mechanical relay actually has a higher time constant and its movable contacts move with higher speed than the high speed siphon recorders usually employed in work of this nature.

Assuming a dot impulse occurs 111 a given unit of time, a dash impulse in three of said units of time, a spacing between impulses constituting the same character in one of said units of time, a spacing period between letters in three of said units of time, and a spacing period between words in five of said units of time; a keying cycle may then be said to occur within two of the said units of time.

It has been ascertained by experiment that the average five letter word comprises twentyfour of the above mentioned cycles. Therefore, if sixty words are being transmitted per minute, the keying frequency may be said to be twenty-four cycles; and, if one hundred words are being transmitted per minute, the keying frequency may be said to be forty cycles. Every transmitting rate may therefore be said to have its corresponding keying frequency.

The use of mechanical transmitters for keying signals in a wired telegraph system or to the radio transmitting device has become very common practice where high speed transmission is desired. When such transmitters are employed, the dots. dashes and spacing periods are formed with great accuracy and it is important that the receiving apparatus faithfully reproduce these dots, dashes and spacing periods. It is also important that the received signals be clearly differentiated from interference or static.

In order to realize faithful reproduction and amplification of the received signal impulses, the time constant of my improved push-pull amplifying system is chosen to be substantially equal to the reciprocal of the keying frequency employed at the transmitting station. For example, if the signals are beingtransmittcd at a rate of one hundred words per minute, the condensers C and C with their related resistances and R will be so adjusted that the transient pulses in the output of the system Will correspond very closely to the keying cycle of the transmitted signal.

Referring to Fig. 6, curve 6 shows the received pulses impressed on the grid filament circuits of the triodes T and T Curve f shows the amplified pulses in the output circuits of the triodes corresponding to the pulses of curve e. The above described amplifying system is arranged to oscillate very slightly at a frequency substantially equal to the keying frequency employed at the transmitting station. The biasing batteries C and C Will prevent the triodes T and T from oscillating in any other manner. This imparts a gently swinging characteristic to the output circuits of the triodes T and T as seen in curve 7,

- which with continued signalling, is adjusted to be substantially in phase with the keying frequency. These gentle swings are in themselves insufficient to actuate the relay armature 13; but they will substantially aid in the faithful reproduction of the desired signal impulses and will oppose out of phase disturbances as shown.

When the amplitude of an amplified received signal pulse attains a value located within the zone 9 of curve f, the relay armature definitely makes a marking or spacing contact and holds the same until the amplitude again attains a value within the zone 9 of a succeeding portion of the signal pulse. This results 'in very much improved and clear: cut signal pulses from the'relay 5 as shown by the curve h of Fig. 6. It isxtherefore obvious from the above discussion that the adjustment of the time constant of the amplifying system to the keying frequency results in considerably improved and clear-cut signal pulses with'the substantial elimination of the effects of various disturbances on the amplified signal pulses.

My amplifying system is especially useful in the operation of 'signal printing devices and other si al responsive devices requiring definite mar ing and spacing pulses with as great a suppression of disturbances as possible for their successful functioning. My improved amplifying system is also especially useful in re-transmission systems where it is ,few applications of my improved amplifying system, I wish it distinctly understood that .said applications are merely cited by way of examples as there are many other applications which might be made.

1 Ohms Volts M. F.

Conditions R: R: R: R4 R: B; B1 B: C C C1 C2 Condition 1 corresponds to the case where faithful reproduction and amplification of all of the pulses impressed on the amplifylng system are desired. Condition 2 corresponds to the case where faithful reproduction and amplification of the signal pulses and the minimizing of .the effects of interferingpulses are desired when the signals are transmitted at a keying frequency of 40 cycles (100 words per minute). Condition 3 corresponds to the case where faithful reproduction and amplification of the signal pulses and the minimizing of the effects of disturbing pulses are desired when the signals are transmitted at a frequency of 24 cycles (corresponding to 60 wordsper minute).

The values in the above table are given merely for the purpose of enabling those skilled in the art to practice the invention and it is to be distinctly understood that I do not limit myself to these values. It is also obvious that the capacitiesof the condensers C and C and the values of the various resistances and batteries may beso chosen .as to effect the faithful reproduction and amplification ofthe signal pulses transmitted at keyling frequencies other than 24 cycles and 40 c 0 es.

While I have shown and described a preferred embodiment of my invention I do not limit myself to the same but may employ such other embodiments as come within the spirit and scope of my invention.

Having described my invention, what I claim is:

1. The combination with means for receivingsignal impulses comprising resonant circuits of means for faithfully reproducing and amplifying said signal impulses comprising means comprising circuits having adjustable time constants and a double winding relay for producing amplified signal impulses, the amplified signal impulses being substantially in phase with the received signal impulses for a considerable range of keying frequencies. 1 2. The combination with means for receiving electrical impulses comprising receiving circuits of means for faithfully reproducing and amplifying said impulses comprising a pair of resistances connected thereto and producing a voltage drop corresponding to said signal impulses, a pair of balanced amplifier devices connected thereto, a double winding relay having its windings respectively connected to said triodes and time controlled means for maintaining biasing potentials on the grids of said triodes at different values.

3. The combination with means for receiving electrical impulses including both signalling impulses and disturbing impulses of means for faithfully reproducing and amplifying substantially all of said impulses comprising vacuum tube circuitsjhavingadjustable time constants cooperating therewith, a mechanical relay actuated thereby, and means for applying differential biases upon the grids of said tubes for holding said relay in a biased position. v

4. The combination with means for receiving signal impulses and disturbing impulses bearing certain predetermined relationships tothe signal impulses of means for faithfully reproducing and amplifying the signal impulses and substantially eliminating the effects of the disturbing impulses comprising resistance input means, a pair of balanced differentially biased triode amplifier devices connected thereto through a pair of locking resistances adapted supply a supplemental bias to said amplifiers and a mechanical relay operated thereby.

5. In a signal reproducing device, the combination of resistance input means, a pair of differentially biased triode amplifiers, a me chanical relay associated with the output circuit of each of said triodes and resistance means for locking said arrangement whereby signal impulses of a current strength below a predetermined value have no effect on the current passed through said triode amplifiers and produces no action in said relay.

6. The combination with means responsive to weak and uncertain signal impulses of means for producing strong and purified amplified impulses from sai signal impulses comprising a pair of balanced triode amplifier devices, a resistance input means therefor, a'mechanical relay operated thereby, differential grid bias means connected thereto and means for producing a strong current change to move said relay followed by a weaker holding current. i

7. The combination with means responsive to signal impulses comprising a non-oscillating relayof an amplifying system cooperating therewith and having its time constant adjusted to bear a predetermined relationship to the keying frequency of the transmitted signal impulses.

8. The combination with a non-resonant mechanical relay and associated triode ampli output circuits of said 'triodes and associated with said relay whereby said relay action upon the triode passing current is considerably accentuated 9. .In a signal repeater, the combination of a pair of balanced amplifier devices, a nonoscillating relay actuated thereby, and time controlled grid bias means for controlling the initial pulse of current supplied to said relay in response to signal changes passing through a critical amplitude zone.

10. The method of receiving signals and excluding static interference which consists in actuating a relay by means of balanced triode amplifier devices having differential grid bias means, whereby said relay is caused to respond quickly to signal impulses above a definite value and to be unresponsive to impulses below a definite value.

11. The method of controlling the operating characteristics of a mechanical relay which comprises including in its input circuit a triode amplified means and connecting therebetween circuits having a controlled time delay constant for accentuating the action of said relay upon the receipt of current pulses in said amplifier.

12. In a signal repeater the combination of a pairof balanced amplifiers, a non-oscillating relay, and time controlled amplifier grid bias means for controlling the current output of said amplifier and actuating said relay only in response to signal changes passing through a critical amplitude zone, said time controlled means including a capacity and parallel connected resistance in the output circuit of each amplifying device, said means being connected between said amplifying devices and said relay.

13. In a signal indicating system, the combination of a differential relay and a pair of vacuum tubes having plate circuits for actuating the relay differentially associated therewith, means for biasing the grids of said tubes to normally close the relay on one of its contacts, means for oppositely modifying the bias of said grids to change the relative values of the currents in the plate circuits of said tubes to close the relay on its other contact, and a condenser with a charging resistance in parallel therewith in the plate circuit of each tube for momentarily accentuating the change in the plate currents.

14. In a signal indicating system the combination of a differential relay and a pair of vacuum tubes having plate circuits for actuating the relay and differentially associated therewith of, means for biasing the grids of said tubes to normally close the relay on one of its contacts, means for oppositely modify- I ing the bias on the grid of the second tube for ond tube for aiding the action of said relay and means connected in the plate circuit of each tube and common to the grid circuit of the other tube for presenting an extra bias on the grid of said tube members whereby disturbing influences in signal reception not reaching a predetermined current value pro duce no efiect on said relay.

15. In a signal indicating system, a source of received signals, a pair of vacuum tubes resistively and differentially connected thereto, means for biasing the grids of said tubes, whereby one tube is passing current on conditions of no signal pulses and the other tube passes current at a time when signal pulses are received, a differential relay connected in the plate circuit of said tubes, and means in the plate circuit of each of said tubes for accentuating the initial pulse of current through said tubes, whereby the speed oi relay action upon receipt of incoming signals is considerably aided.

16. In a signal indicating system, the combination of a pair of differentially biased triode amplifiers, a double acting relay connected in the output circuit of said, tubes, whereby the relay marks dots -or dashes and spaces in accordance with which of said tubes pass current, a separate source of a plate current for each of said differentially biased triodes, and means actuated by the receipt of signals from a source for oppositely modifying the bias on the grids of said tubes, whereby the strength of current flowing through is increased in one of said tubes and decreased through the other of said tubes, and means connected in the platecircuit of each of said tubes for momentarily accentuating the RICHARD H. RANGER; 

